Laser threat warning receivers must have wide fields of view in order to determine the direction of laser radiation from a distant source. However, it is also desirable that such receivers have high sensitivity and angular resolution so that the direction of the distant laser source can be determined. In the prior art, a slit aperture has been used in order to pass the radiation to a curved array of detectors. Because the detectors are not in a flat plane, however, the manufacturing of such devices is not as simple as has been desired. Further, as no optical elements are used to increase the density of radiation on the detectors, sensitivity is thereby limited. Where wide fields of view are of concern, the focusing of radiation onto a flat plane with a small image blur, prior to the present invention, has been a difficult problem, and no simple rugged system for use in determining the direction of such distant sources over wide fields of view is known.